You should read this book if you want to do any development for KDE.
We're using the term development very broadly to cover anything that can lead to a change in source code. This includes:
Submitting a bug fix
Writing a new application powered by KDE technology
Contributing to an existing project
Adding functionality to KDE development libraries
In this book we'll give you the basics you need to be a productive
We'll explain the tools you should install, show you how to
read the documentation (and write your own, once you've created new
functionality!) and how to get help in other ways. We'll introduce you
to the KDE community, which is key to understanding KDE because we are a
free, open source project.